The Experts below are selected from a list of 7470 Experts worldwide ranked by ideXlab platform
Martin Muschol - One of the best experts on this subject based on the ideXlab platform.
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Action spectra of electrochromic voltage-sensitive dyes in an intact Excitable Tissue
Biophysical Journal, 2009Co-Authors: Joseph Foley, Martin MuscholAbstract:Voltage-sensitive dyes VSDs provide a spatially resolved optical read-out of electrical signals in Excitable Tissues. Several com- mon fluorescent VSDs display electrochromic shifts of their emission spectra, making them suitable candidates for ratiometric measure- ments of transmembrane voltages. These advantages of VSDs are tem- pered by Tissue-specific shifts to their fluorescence emission. In addi- tion, the optimal electrochromic dye response occurs in wavelength bands distinct from the dye's maximal resting emission. This "action spectrum" can undergo Tissue-specific shifts as well. We have devel- oped a technique for in situ measurements of the action spectra of VSDs in intact Excitable Tissues. Fluorescence emission spectra of VSDs during action-potential depolarization were obtained within a single sweep of a spectrophotometer equipped with a change-coupled device CCD array detector. To resolve the subtle electrochromic shifts in voltage-induced dye emission, fluorescence emission spectra measured right before and during field-induced action-potential de- polarization were averaged over about 100 trials. Removing white- noise contributions from the spectrometer's CCD detector/amplifier via low-pass filtering in Fourier space, the action spectra of all dyes could be readily determined. © 2008 Society of Photo-Optical Instrumentation En-
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Action spectra of electrochromic voltage-sensitive dyes in an intact Excitable Tissue.
Journal of biomedical optics, 2008Co-Authors: Joseph Foley, Martin MuscholAbstract:Voltage-sensitive dyes (VSDs) provide a spatially resolved optical read-out of electrical signals in Excitable Tissues. Several common fluorescent VSDs display electrochromic shifts of their emission spectra, making them suitable candidates for ratiometric measurements of transmembrane voltages. These advantages of VSDs are tempered by Tissue-specific shifts to their fluorescence emission. In addition, the optimal electrochromic dye response occurs in wavelength bands distinct from the dye's maximal resting emission. This "action spectrum" can undergo Tissue-specific shifts as well. We have developed a technique for in situ measurements of the action spectra of VSDs in intact Excitable Tissues. Fluorescence emission spectra of VSDs during action-potential depolarization were obtained within a single sweep of a spectrophotometer equipped with a change-coupled device (CCD) array detector. To resolve the subtle electrochromic shifts in voltage-induced dye emission, fluorescence emission spectra measured right before and during field-induced action-potential depolarization were averaged over about 100 trials. Removing white-noise contributions from the spectrometer's CCD detector/amplifier via low-pass filtering in Fourier space, the action spectra of all dyes could be readily determined.
T J Obrien - One of the best experts on this subject based on the ideXlab platform.
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properties of an intermediate duration inactivation process of the voltage gated sodium conductance in rat hippocampal ca1 neurons
Journal of Neurophysiology, 2016Co-Authors: Elisa L Hillyardin, T J Obrien, Zhen Zeng, Christopher A French, David A. WilliamsAbstract:Rapid transmembrane flow of sodium ions produces the depolarizing phase of action potentials (APs) in most Excitable Tissue through voltage-gated sodium channels (NaV). Macroscopic currents display rapid activation followed by fast inactivation (IF) within milliseconds. Slow inactivation (IS) has been subsequently observed in several preparations including neuronal Tissues. IS serves important physiological functions, but the kinetic properties are incompletely characterized, especially the operative timescales. Here we present evidence for an “intermediate inactivation” (II) process in rat hippocampal CA1 neurons with time constants of the order of 100 ms. The half-inactivation potentials ( V 0.5) of steady-state inactivation curves were hyperpolarized by increasing conditioning pulse duration from 50 to 500 ms and could be described by a sum of Boltzmann relations. II state transitions were observed after opening as well as subthreshold potentials. Entry into II after opening was relatively insensitive to membrane potential, and recovery of II became more rapid at hyperpolarized potentials. Removal of fast inactivation with cytoplasmic papaine revealed time constants of I Na decay corresponding to II and IS with long depolarizations. Dynamic clamp revealed attenuation of trains of APs over the 102-ms timescale, suggesting a functional role of II in repetitive firing accommodation. These experimental findings could be reproduced with a five-state Markov model. It is likely that II affects important aspects of hippocampal neuron response and may provide a drug target for sodium channel modulation.
Joseph Foley - One of the best experts on this subject based on the ideXlab platform.
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Action spectra of electrochromic voltage-sensitive dyes in an intact Excitable Tissue
Biophysical Journal, 2009Co-Authors: Joseph Foley, Martin MuscholAbstract:Voltage-sensitive dyes VSDs provide a spatially resolved optical read-out of electrical signals in Excitable Tissues. Several com- mon fluorescent VSDs display electrochromic shifts of their emission spectra, making them suitable candidates for ratiometric measure- ments of transmembrane voltages. These advantages of VSDs are tem- pered by Tissue-specific shifts to their fluorescence emission. In addi- tion, the optimal electrochromic dye response occurs in wavelength bands distinct from the dye's maximal resting emission. This "action spectrum" can undergo Tissue-specific shifts as well. We have devel- oped a technique for in situ measurements of the action spectra of VSDs in intact Excitable Tissues. Fluorescence emission spectra of VSDs during action-potential depolarization were obtained within a single sweep of a spectrophotometer equipped with a change-coupled device CCD array detector. To resolve the subtle electrochromic shifts in voltage-induced dye emission, fluorescence emission spectra measured right before and during field-induced action-potential de- polarization were averaged over about 100 trials. Removing white- noise contributions from the spectrometer's CCD detector/amplifier via low-pass filtering in Fourier space, the action spectra of all dyes could be readily determined. © 2008 Society of Photo-Optical Instrumentation En-
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Action spectra of electrochromic voltage-sensitive dyes in an intact Excitable Tissue.
Journal of biomedical optics, 2008Co-Authors: Joseph Foley, Martin MuscholAbstract:Voltage-sensitive dyes (VSDs) provide a spatially resolved optical read-out of electrical signals in Excitable Tissues. Several common fluorescent VSDs display electrochromic shifts of their emission spectra, making them suitable candidates for ratiometric measurements of transmembrane voltages. These advantages of VSDs are tempered by Tissue-specific shifts to their fluorescence emission. In addition, the optimal electrochromic dye response occurs in wavelength bands distinct from the dye's maximal resting emission. This "action spectrum" can undergo Tissue-specific shifts as well. We have developed a technique for in situ measurements of the action spectra of VSDs in intact Excitable Tissues. Fluorescence emission spectra of VSDs during action-potential depolarization were obtained within a single sweep of a spectrophotometer equipped with a change-coupled device (CCD) array detector. To resolve the subtle electrochromic shifts in voltage-induced dye emission, fluorescence emission spectra measured right before and during field-induced action-potential depolarization were averaged over about 100 trials. Removing white-noise contributions from the spectrometer's CCD detector/amplifier via low-pass filtering in Fourier space, the action spectra of all dyes could be readily determined.
Ernest A Jennings - One of the best experts on this subject based on the ideXlab platform.
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scorpion toxin peptide action at the ion channel subunit level
Neuropharmacology, 2017Co-Authors: David M Housley, Gary D Housley, Michael J Liddell, Ernest A JenningsAbstract:This review categorizes functionally validated actions of defined scorpion toxin (SCTX) neuropeptides across ion channel subclasses, highlighting key trends in this rapidly evolving field. Scorpion envenomation is a common event in many tropical and subtropical countries, with neuropharmacological actions, particularly autonomic nervous system modulation, causing significant mortality. The primary active agents within scorpion venoms are a diverse group of small neuropeptides that elicit specific potent actions across a wide range of ion channel classes. The identification and functional characterisation of these SCTX peptides has tremendous potential for development of novel pharmaceuticals that advance knowledge of ion channels and establish lead compounds for treatment of Excitable Tissue disorders. This review delineates the unique specificities of 320 individual SCTX peptides that collectively act on 41 ion channel subclasses. Thus the SCTX research field has significant translational implications for pathophysiology spanning neurotransmission, neurohumoral signalling, sensori-motor systems and excitation-contraction coupling.
Christopher A French - One of the best experts on this subject based on the ideXlab platform.
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properties of an intermediate duration inactivation process of the voltage gated sodium conductance in rat hippocampal ca1 neurons
Journal of Neurophysiology, 2016Co-Authors: Elisa L Hillyardin, T J Obrien, Zhen Zeng, Christopher A French, David A. WilliamsAbstract:Rapid transmembrane flow of sodium ions produces the depolarizing phase of action potentials (APs) in most Excitable Tissue through voltage-gated sodium channels (NaV). Macroscopic currents display rapid activation followed by fast inactivation (IF) within milliseconds. Slow inactivation (IS) has been subsequently observed in several preparations including neuronal Tissues. IS serves important physiological functions, but the kinetic properties are incompletely characterized, especially the operative timescales. Here we present evidence for an “intermediate inactivation” (II) process in rat hippocampal CA1 neurons with time constants of the order of 100 ms. The half-inactivation potentials ( V 0.5) of steady-state inactivation curves were hyperpolarized by increasing conditioning pulse duration from 50 to 500 ms and could be described by a sum of Boltzmann relations. II state transitions were observed after opening as well as subthreshold potentials. Entry into II after opening was relatively insensitive to membrane potential, and recovery of II became more rapid at hyperpolarized potentials. Removal of fast inactivation with cytoplasmic papaine revealed time constants of I Na decay corresponding to II and IS with long depolarizations. Dynamic clamp revealed attenuation of trains of APs over the 102-ms timescale, suggesting a functional role of II in repetitive firing accommodation. These experimental findings could be reproduced with a five-state Markov model. It is likely that II affects important aspects of hippocampal neuron response and may provide a drug target for sodium channel modulation.
